Medium-Entropy Alloy MoCoCu-P as an Efficient Bifunctional Catalyst for Water Splitting.

Medium/high-entropy alloy (MEA/HEA) catalysts have emerged as ideal candidates as multi-functional catalysts owing to their synergistic effects of multiple metal components on the boosted catalytic activity. However, the facile preparation and screening of suitable MEAs element to achieve high catalytic performance still remain challenging. In this work, we successfully synthesized a MoCoCu-P MEA electrocatalyst for water splitting electrocatalysis through a feasible electrodeposition method. The as-prepared MEA demonstrated an overpotential of 276.1mV (j=10mA/cm²) for OER with a Tafel slope of 38.3mV/dec, coupled with an overpotential of 64.7mV for HER (j=10mA/cm²) with a Tafel slope of 87.7mV/dec. Employed in an overall water electrolysis cell, MEA achieved a nearly 100% Faradaic efficiency and superior stability over than 50hours at a high current density of 50mA/cm2. X-ray photoelectron spectroscopy (XPS) analysis verify that high-valence Co and Mo are the most active sites for OER, while electron-rich Cu at the presence of P is responsible for the boosted HER in the MoCoCu-P MEA. This study not only provides a feasible electrodeposition strategy to obtain MEA catalysts with high activity and excellent stability, but also sheds fundamental lights on the identification of the active sites in MEA catalysis.